Osmoscope is used for

Osmosis is the process of movement of water across a semipermeable membrane along the concentration gradient. Osmoscope is used to demonstrate the process of osmosis. Usually a potato osmoscope is used in which a sugar solution is placed  inside a cavity carved out in a potato tuber, which is kept in water. After some time due to osmosis level of solution inside the cavity rises, because water from surrounding cells enter the cavity.